This invention relates to rolling or sliding machine parts such as bearings, thrust plates or gears.
Some machine parts make rolling motions while others make sliding motions. In the following description, these motions are referred to as "rolling or sliding motions".
Machine parts which have rolling or sliding motions may suffer damage to their surfaces if an oil film runs out at the contact portion with a mating member due to insufficient lubrication and as a result the machine part is brought into direct contact with the mating member.
To prevent such surface damage due to loss of oil film at the contact portion, conventional machine parts have their surfaces finished as smoothly as possible.
To finish the surfaces as smoothly as possible, they are usually mirror-finished. But mirror finish is a time-consuming and expensive solution.
Today's machine parts are lubricated by less viscous lubricants to reduce friction loss. Also, they are often used in a high-temperature environment and operated at high speeds. Due to these factors, it is becoming more and more difficult to form a sufficiently thick oil film at the contact portion. Thus, even if the surface roughness of the machine part is reduced to the limit by mirror finishing, it is difficult to completely prevent direct contact with the mating member.
An object of the present invention is to provide a rolling or sliding machine part which has an improved surface that permits the formation of a thick oil film thereon so as to provide a long part life.